The present invention relates to bracing for building frames, and, more particularly, to a washer assembly that is especially useful to secure braces to metal building frames.
Typically, the frames of metal buildings are stabilized with bracing--most often with rod or cable braces. FIG. 1 is a graphic representation of a typical metal building frame 1, with diagonal rod or cable braces 2 between the wall columns 4 and roof purlins 3 of frame 1. Braces 2 stiffen frame 1 (a) to enhance the ability of frame 1 to resist both lateral forces exerted against frame 1 by, for example, wind and earthquakes and the effects of the loads placed on frame 1 by cranes and other heavy equipment operating in frame 1, (b) to minimize building vibrations, and (c) to facilitate construction of frame 1. Concentrated loads on braces 2 are transferred by "hillside washers" directly to the webs of purlins and columns 3 and 4.
FIG. 2 shows typical prior art rod and cable bracing used in the industry, which employ "hillside washers." FIG. 2A shows the details of a rod brace assembly 5 mounted to the web 6 of a vertical column 4 of frame 1. Rod brace assembly 5 includes a rod brace 7 the threaded end 9 of which is mounted to web 6 using a "hillside washer" 8, a flat washer 10, and a hex nut 11. The remaining end (not shown) of brace 7 is typically bolted diagonally to another wall column 4 or roof purlin 3 of frame 1. End 9 of brace 7 is inserted through a hole formed in web 6 to an extent that leaves a length of threaded end 9 exposed that is sufficient to permit threading of hillside washer 8, flat washer 10 and hex nut 11 onto end 9 to mount brace 7 to web 6. Hillside washer 8 allows for the transfer of the load from brace 2 to web 6 through washer 10 and nut 11.
FIG. 2B shows the details of a prior art assembly 16 that is identical to assembly 5 with the exception that assembly 16 includes an eye bolt 18, which is mounted to hillside washer 8, flat washer 10 and hex nut 11, and cable 19 instead of a brace 7. One end of cable 19 is secured through the eye of eye bolt 18.
FIG. 3 shows the standard, prior art hillside washer. Washer 8 defines a tab 13 that extends through a correspondingly shaped slot formed in web 6 when washer 8 is mounted in place to stabilize the radial position of washer 8. Semicircular members 14 provide a bearing surface for washer 10 that permits mounting rod 7 at a variety of angles to web 6. Oversized opening 15 permits the mounting of rod 7 to hillside washer 8 at a variety of angles to hillside washer 8. The shape of hillside washer 8 permits it to be oriented so that flat surface 12 of hillside washer 8 bears against web 6.
Unfortunately, these assemblies often fail under load conditions. In some instances, the webs of the columns fail at the point at which the bracing is mounted to the web due to the load transferred to the web by the bracing. Also, the bearing surface between the flat washer and the hillside washer causes problems. In particular, a very small area of the hillside washer is in contact with the surface of the flat washer. Consequently, the load from the bracing is concentrated on a very small surface area of the hillside washer, which often causes the hillside washer to fracture and allow the rod to be pulled through the washer. Also, the flat washer can slip on the surface of the curved semicircular members 14, allowing unwanted movement of the bracing and building frame members. In some instances, the hillside washer itself is pulled through the web. This problem has been addressed through the use of a flat bearing plate that is positioned between the base of the hillside washer and the web, in an effort to distribute the load over a larger area of the column.
There exists, therefore, a need for a washer assembly for building frame bracing that is less prone to fracturing and that provides greater stability.